Conventionally, there has been a demand for a device to confirm the geographical location of a present position and provide guidance on the route to a target position by a map. As a device satisfying such demand, car navigation systems are known (for example Patent Document 1, Patent Document 2, and Patent Document 3).
In general, a car navigation system calculates the geographical location of the present position by receiving and processing signals transmitted from a plurality of GPS (global positioning system) satellites (hereinafter described as “GPS signals”), reads out map data on the surroundings of this present position from a database stored in a storage unit (DVD, hard disc, etc.) in the system, and displays it on a display. Further, a path of movement of a vehicle is calculated by using a car speed sensor and a gyro sensor, map matching processing for detecting a degree of coincidence between this and a road on the map is carried out, and error of the position finding is corrected.
However, there is a demand for a user to determine his own location and learn the route up to the target position even when he is not in a vehicle. As a device satisfying such a demand, a mobile cellular phone mounting a simple map information display processing function has appeared.
Initially, mobile cellular phones equipped with map information display processing functions lacked a device for measuring the bearing, therefore a map display easily understood by the user such as a heading up display (display rotating the map so that an advancing direction was directed toward the top of a screen) which was generally performed in a car navigation system was difficult.
Therefore, in recent years, a mobile cellular phone equipped with a map information display processing function measuring the bearing by using a geomagnetic sensor and enabling heading up display has been proposed.
Patent Document 1: Japanese Patent Publication (A) No. 2004-28837
Patent Document 2: Japanese Patent Publication (A) No. 2002-328042
Patent Document 3: Japanese Patent Publication (A) No. 10-197258